The present disclosure relates generally to coaxial-to-stripline transitions and stripline-to-stripline transitions, and more particularly coaxial-to-stripline and stripline-to-stripline transitions including a shorted center via.
Coaxial-to-stripline and stripline-to-stripline transitions are often used in both radiating and non-radiating electromagnetic (EM) devices, for example, radar seeker antennas and circuit card assemblies. These EM devices may contain one or more layers of a stripline transmission line medium and one or more sections of a coaxial transmission line medium. EM energy inside these devices may be channeled throughout the assembly via one or more stripline-to-stripline or coaxial-to-stripline transitions. These transitions must couple electromagnetic energy smoothly between stripline layers and from the stripline layers to the coaxial mediums with relatively low energy loss and a low incidence of reflections at the desired operating frequencies.
Some coupling mechanisms for stripline-to-coaxial and stripline-to-stripline transitions may require manufacturing techniques that are relatively labor intensive and time consuming, or that may require detailed assembly. For example, blind-plated and buried-plated vias located within a stripline may be used, which require relatively precise manufacturing techniques and tolerances. Laser ablation techniques may be used to form such blind or buried vias; however, this process is not capable of achieving the same aspect ratios as plated through vias, and further requires an additional manufacturing step. Back-drilling and filling techniques may also be used to turn a through via into either a blind or a buried via. However, drill depth can be difficult to control, which may leave stubs that may de-tune the transition. Therefore, the formation of blind or buried vias may be a relatively expensive, complex process and may not be capable of meeting the positional tolerances and aspect ratios that may be achieved by through vias.